5b. The Facial Bones. 1. The Nasal Bones

FIG. 154 Articulation of nasal and lacrimal bones with maxilla.

(Ossa Faciei) & (Ossa Nasalia)

The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, the bridge of the nose (Fig. 190). Each has two surfaces and four borders.

Surfaces.The outer surface (Fig. 155) is concavoconvex from above downward, convex from side to side; it is covered by the Procerus and Compressor naris, and perforated about its center by a foramen, for the transmission of a small vein. The inner surface (Fig. 156) is concave from side to side, and is traversed from above downward, by a groove for the passage of a branch of the nasociliary nerve.

Borders.The superior border is narrow, thick, and serrated for articulation with the nasal notch of the frontal bone. The inferior border is thin, and gives attachment to the lateral cartilage of the nose; near its middle is a notch which marks the end of the groove just referred to. The lateral border is serrated, bevelled at the expense of the inner surface above, and of the outer below, to articulate with the frontal process of the maxilla. The medial border, thicker above than below, articulates with its fellow of the opposite side, and is prolonged behind into a vertical crest, which forms part of the nasal septum: this crest articulates, from above downward, with the spine of the frontal, the perpendicular plate of the ethmoid, and the septal cartilage of the nose.

FIG. 155 Right nasal bone. Outer surface.

FIG. 156 Right nasal bone. Inner surface.

Ossification.Each bone is ossified from one center, which appears at the beginning of the third month of fetal life in the membrane overlying the front part of the cartilaginous nasal capsule.

Articulations.The nasal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the opposite nasal and the maxilla.